4-Hydroxyacetophenone (4-HAP) is a possible intermediate for a variety of products having a multiplicity of end uses. Thus, U.S. Pat. No. 4,524,217, issued June 18, 1985 to Davenport et al, discloses a process for using 4-HAP to make N-acetyl-para-aminophenol (APAP) better known as acetaminophen, which has wide use as an analgesic. Pending U.S. application Ser. No. 06/627,381, filed July 3, 1984, discloses the use of 4-HAP as an intermediate for the production of 4-acetoxyacetanilide (4-AAA) which can be used for the preparation of poly(ester-amide)s capable of forming an anisotropic melt phase and suitable for being formed into shaped articles such as moldings, fibers and films. In addition, 4-AAA may also be hydrolyzed to form APAP. Pending U.S. application Ser. No 06/633,831, filed July 24, 1984, discloses a process wherein 4-HAP is used to produce 4-acetoxybenzoic acid (4-ABA) which is also capable of being used directly to make polymers which can be formed into an anisotropic melt suitable for the formation of shaped articles. Moreover, 4-ABA can be hydrolyzed to 4-hydroxybenzoic acid (4-HBA) which can be used as an intermediate for the production of preservatives, dyes, and fungicides. Pending U.S. applications Ser. No. 06/661,552, filed Oct. 17, 1984, and Ser. No. 06/689,533, filed Jan. 7, 1985, disclose processes wherein 4-HAP is used as an intermediate for the production of hydroquinone (HQ) which has utility as a photographic developer, polymerization inhibitor, dye intermediate, and anti oxidant.
Various U.S. patent disclosures teach processes for the production of 4-HAP by the Friedel-Crafts acetylation of phenol utilizing hydrogen fluoride as catalyst and reaction conditions within certain prescribed ranges. These include pending applications Ser. Nos. 06/714,407 filed Mar. 21, 1985 and 06/721,007 filed Apr. 8, 1985 which show acetic anhydride as acetylating agent, 06/716,016 filed Mar. 26, 1985 which shows acetic acid as acetylating agent and 06/616,989, filed June 4, 1984 which shows various acetylating agents including both acetic acid and anhydride and also discloses the production of 4-HAP by the Fries rearrangement of phenyl acetate with hydrogen fluoride catalyst. The entire disclosures of these applications are incorporated herein by reference.
While the foregoing and similar processes have the advantage of producing 4-HAP in relatively high yields, the crude product before purification contains an amount of hydrogen fluoride (HF), most of which must be removed and recycled for reasons of economy, and also to obtain a 4-HAP suitable for subsequent use. Some of the HF may be removed by straight distillation under relatively mild conditions. However, because of the apparent formation of a stable and relatively high boiling complex of 4-HAP and HF, removal of sufficient HF necessary to obtain a 4-HAP of suitable purity requires distillation under vacuum at temperatures so high as to cause an unfavorable loss of 4-HAP due to polymerization or other side reactions. Thus, any process which achieves a satisfactory level of separation of HF from 4-HAP without undue loss of 4-HAP is very desirable.
Simons et al, Journal of the American Chemical Society, 62, 485 and 486 (1940) show the use of hydrogen fluoride as a condensing agent for various rearrangements and at page 486 show the Fries rearrangement of phenyl acetate to obtain p-hydroxyacetophenone.
Dann and Mylius in a dissertation included as part of a series of Reports from the Institute for Applied Chemistry of the University of Erlangen, received for publication on Jan. 7, 1954 and published in Annalen der Chemie 587 Band, pages 1 to 15, disclose the reaction of phenol and glacial acetic acid in the presence of hydrogen fluoride to produce 4-hydroxyacetophenone (4-HAP) in a yield of 61.6%. This reaction may be conventionally characterized as a Friedel-Crafts acetylation of phenol with acetic acid as the acetylating agent.
Simons et al, Journal of the American Chemical Society, 61, 1795 and 1796 (1939) teach the acylation of aromatic compounds using hydrogen fluoride as a condensing agent and in Table 1 on page 1796 show the acetylation of phenol with acetic acid to produce p-hydroxyacetophenone (4-HAP) in 40% yield.
Davenport et al, U.S. Pat. No. 4,524,217 discloses a process of making an N-acyl-hydroxy aromatic amine such as N-acetyl-para-aminophenol (APAP or acetaminophen) by reacting a hydroxy aromatic ketone such as 4-HAP with a hydroxylamine salt and a base to obtain the ketoxime of the ketone, e.g. 4-HAP oxime, and subjecting the ketoxime to a Beckmann rearrangement to form the N-acyl-hydroxy aromatic amine. The hydroxy aromatic ketone may be prepared by the Fries rearrangement of a phenolic ester, e.g. phenyl acetate or the Friedel-Crafts acylation of a phenolic compound, e.g. phenol, with an acylating agent, e.g. acetic acid or anydride, using hydrogen fluoride as a catalyst.
European Patent No. 102,297 teaches a process of recovering ortho-benzoyl benzoic acid, hydrogen fluoride and boron trifluoride from a complex of these compounds by subjecting the complex to the action of an inert solvent in a distillation column. The inert solvent may be a halogenated hydrocarbon such as methylene chloride or 1,2-dichloroethane, or a fluorinated aromatic hydrocarbon.